ASTM D4824-24

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4824 − 24
Standard Test Method for
Determination of Catalyst Acidity by Ammonia
1
Chemisorption
This standard is issued under the fixed designation D4824; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This test method involves the measurement of total catalyst acidity by chemisorption of ammonia
in a static volumetric system. Acidity is a very important property in determining catalyst activity and
selectivity in many commercial reactions. Zeolite based catalysts used in the petroleum industry for
catalytic cracking are a prime example. This test method describes a simple procedure employing
inexpensive equipment that could readily be assembled in most laboratories.
1. Scope E122 Practice for Calculating Sample Size to Estimate, With
Specified Precision, the Average for a Characteristic of a
1.1 This test method covers the determination of acidity of
Lot or Process
catalysts and catalyst carriers by ammonia chemisorption. A
E691 Practice for Conducting an Interlaboratory Study to
volumetric measuring system is used to obtain the amount of
Determine the Precision of a Test Method
chemisorbed ammonia.
3. Terminology
1.2 The values stated in SI units are to be regarded as
standard. The values given in parentheses after SI units are
3.1 Definitions—See Terminology D3766.
provided for information only and are not considered standard.
3.2 Symbols:
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3
V = calibrated expansion volume, cm .
responsibility of the user of this standard to establish appro-
k
T = temperature of V at initial ammonia pressure, K.
priate safety, health, and environmental practices and deter-
1 k
T = temperature of V at final ammonia pressure, K.
mine the applicability of regulatory limitations prior to use. 2 k
P = initial ammonia pressure, torr.
1
1.4 This international standard was developed in accor-
P = final ammonia pressure, torr.
2
dance with internationally recognized principles on standard-
W = mass of sample, g.
s
ization established in the Decision on Principles for the
W = tare of sample tube, g.
1
Development of International Standards, Guides and Recom-
W = sample mass plus tare of tube, g.
2
mendations issued by the World Trade Organization Technical
P = initial ammonia pressure corrected to standard
1T
Barriers to Trade (TBT) Committee.
temperature, torr.
P = final ammonia pressure corrected to standard
2T
2. Referenced Documents
temperature, torr.
2
2.1 ASTM Standards:
4. Summary of Test Method
D3766 Terminology Relating to Catalysts and Catalysis
E105 Guide for Probability Sampling of Materials 4.1 A sample is degassed by heating under vacuum to
remove adsorbed vapors from the surface. The sample is then
exposed to an excess of gaseous ammonia and the excess
1
This test method is under the jurisdiction of ASTM Committee D32 on
ammonia is removed by freezing it into a trap cooled with
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
liquid nitrogen. The chemisorbed ammonia is calculated as the
Chemical Properties.
difference between the volume of ammonia before exposure
Current edition approved Feb. 1, 2024. Published February 2024. Originally
approved in 1988. Last previous edition approved in 2018 as D4824 – 13 (2018).
and the volume recovered in the liquid nitrogen trap.
DOI: 10.1520/D4824-24.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5. Significance and Use
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.1 This test method can be used to determine the acidity of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. catalysts and catalyst carriers by ammonia chemisorption for
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D4824 − 24
materials specifications, manufacturing control, and research 6.1.13 Drying Tube, for drying ammonia gas (for example,
and development in the evaluation of catalysts. a 3A molecular sieve or BaO).
7. Sampling
6. Apparatus
7.1 A test sample shall be obtained from larger composites
6.1 A schematic diagram of one type of apparatus is shown
by riffling or splitting in accordance with subsection 5.12 of
in Fig. 1. It may be constructed of g
...